At present, concrete structures undergo degradation and erosion due to weather, climate and/or their use. This causes these structures to lose their original properties, requiring repair, maintenance or rehabilitation in order to maintain or recover their functionality. This problem affects both floors and walls and ceilings. Therefore, there is a range of products aimed at repair, maintenance or rehabilitation of concrete structures in the market.
For example, concrete correctors can repair cracks, fissures, or detaching concrete floors; while in roofs and walls they can be used for basic repairs, providing that they are not structural. There are some concrete corrective products that, in order to repair the affected area, need a prior application of a primer, a cement base product, and in some cases, a coating to make the surface more resistant. This procedure has a very high cost, requires a more complicated application process, and demands a lot of repair time. There are also many products made with cement and silica sand that are intended for repair in a single step; however, they do not achieve the same curing times, compression resistance, flexibility, durability, nor have a smooth finish. In addition, it should be noted that these products contain free silica that may cause silicosis and lung cancer, and therefore require the use of specialized respiratory masks for protection.
Furthermore, waterproofing products completely block the passage of water and can be applied to ceilings, floors and walls. In particular, they are used for the repair or construction of pools, cisterns and concrete-based reservoirs of water. They can be used both preventively and correctively. However, existing waterproofing agents are polymer-based, that comprise acrylic, vinyl, styrenated thermoplastic resins and copolymers thereof. These waterproofing materials contract and expand with changes in temperature, eventually forming cracks or fissures in the material, which means that the structures and waterproofing materials have to be replaced more frequently.
Finally, the coating can also be applied to ceilings, floors, and walls of concrete structures, which provides greater strength, durability and other characteristics depending on the specific product and use of the concrete structure. Notwithstanding the foregoing, traditional coatings are made with water-based paints. The paints only work well when they are not exposed to water. However, when there is water exposure, they do not offer sufficient durability and require reapplication frequently.
To address this type of technical problem, there are some formulations that seek to partially solve this particular problem. There have been attempts to include additives in the glass-based cement formulation. If the added glass is provided in amorphous form, then the formulation increases its resistance to movement, providing stronger and longer-lasting coatings. However, the application of the product to the surfaces is complicated. On the other hand, if hollow glass microspheres are added, the resulting formulation is lighter but loses compressive strength.
In this connection, there are some prior-art documents referring to the handling of this type of cement formulations. For example, U.S. Pat. No. 3,823,021 discloses an improved cement, which proposes the use of glass particles together with cement and silica. The glass particles proposed in that patent may vary, as ground or pulverized glass particles in a mesh size of 233 to 2.6 of soda-lime glass; or, alternatively like glass microspheres having a diameter of 1678 to 60 microns. The document does not provide for the use of both elements in combination. Therefore, the disadvantage of this invention is that the resulting formulation exhibits the problems discussed in the previous paragraph.
On the other hand, the U.S. patent application US20140047999 discloses a cementitious formulation resistant to acid corrosion and to high temperatures. This formulation defines a cementitious compound formed of several elements and a matrix, wherein the matrix may comprise hollow ceramic microspheres (cenospheres, a light fly-ash fraction) having a specific density of 0.3 to 0.8 g/cm3 and having a particle size of 10-600 microns, typically containing SiO2 (56-64%) and Al2O3 (28-35%). In addition, the matrix is combined with porous recycled glass particles having various particle-sized grades of 8000 to 100 microns. The disadvantage of this document, as mentioned above, is that the addition of hollow glass microspheres results in a lighter formulation, which loses mechanical strength.
Also, patent applications in China address some of these uses as follows. Chinese patent application CN101628801A discloses a heat-insulating mortar, comprised of 8.99 to 15% recycled glass powder and 20 to 40% hollow glass microspheres, in addition to cement and additives. Chinese patent application CN103539391A discloses a waterproofing and heat insulation cement comprising of 8 to 10 parts by weight of recycled glass powder and 18 to 22 parts by weight of hollow glass microspheres, in addition to cement and additives. Chinese patent application CN104893694A discloses a light cement composed of 5 to 15 parts by weight of recycled glass powder having a variable size of 100 to 10 microns and 20 to 30 parts by weight of hollow glass microspheres, in addition to cement and additives. Chinese patent application CN104724983A discloses a different use for the manufacturing of fire-resistant bricks, the formulation of which comprises 4 to 6 parts by weight of recycled glass powder and 2 to 3 parts by weight of hollow glass microspheres, in addition to cement, additives and fibers. The main disadvantage of all these Chinese documents, as specified in previous paragraphs, is that the addition of hollow glass microspheres ultimately produces a lighter formulation, which results in a loss of mechanical strength.
Finally, U.S. Pat. No. 7,335,252 protects a composition which provides for the use of microspheres of any type, either solid or hollow, or a combination of both. The patent focuses on coating mixtures during oil well drilling operations, wherein the coating formulation must be fluid and light in order to be used as the main component for cementing the oil wells. Therefore, this document discloses neither the combination nor addition of the amorphous glass, which furthermore allows for the improvement of the mechanical strength of the structure.
Therefore, the prior art presents a need for a basic formulation that will serve the different products for repair, maintenance or rehabilitation of concrete structures, combining both a greater mechanical resistance and an easy application of the product to the surfaces. It is desirable for the products to have high adhesion to any surface; high compressive and flexural strength; low water absorption; be easy to apply and polish; have a non-cold seal; be resistant to chemicals, not exhibit fissures, and has dimensional and thermal stability in order to prevent contraction and dilation; and that can be sanded, pigmented or painted. Also, it is desirable for the products to be manufactured based on dry powders which make them easier to transport and apply.